Raptor 30 noise...

[Deano]

Okay guys, I need some help pinning down a noise. My heli when I started it up the other day and began to let it warm up made a thumping or a smacking sound. It did it a 2-3 times then I idled up a little more and it did it again but not as loud. When I took off it did it in flight and swung the tail quite a bit. I set it down and decided it was the clutch. Came home and changed both clutch and clutch bell and tried again. same thing. I have noticed that when I hold the bell still, I can move the tail rotor blade assembly some. Not much but I wouldn 't think that there would be any play at all probably around 3-4 degrees. Anyone have any idea what could be causing this??

[flyinfool]

Sounds like a loose belt.
If you set the belt tension in the house and then go out in the cold, the boom will shrink and cause the belt to loosen up.

[Janek]

Yep, I agree, it does sound like a loose and slipping belt

[Deano]

I took the tail off and checked the belt for wear. It look as if it may have been twisted but to be honest, I'm not sure if it was. I reinstalled and made the belt a little tighter and fired it up. I didn't hear the noise but it never left the "warm garage". I will need to try it later outside. By the way, it was around 40 degrees F outside when I last heard the noise. Are you thinking that that is cold enough to shrink the tail boom??

[Janek]

Deano, the belt must have a quarter turn, that's normal, what we were saying is that it was probably just too loose, and needed tightening.

Have you reinstalled it correctly ?, the way to check is to rotate the mainblades, and check that the tails are rotating the correct way round. They don't work too well if running in reverse :lol: :lol: :lol:

[Deano]

It's turning correctly. It looked as if it had maybe 3/4 of a twist in it.

[skatefreak]

Hey.
IT sounds to me like it was indefinitely loose.
Did the noise occur more often during spool up than flight.
The kicking that accompanies the slight "kick" in the tail is renowned for a slipping belt.
If you did in fact have the belt 3/4 turned you would find either noticeable wear on the outside of the belt (if the teeth were facing out wards) or if the teeth were inward facing... no teeth on the belt :p

Just tighten up the belt and it should be fine :)

An overtightened belt on the other hand will sap power from the main blades and cause undue stress on various components...

Have a shot at tightening the belt as you want very little play in the belt either side (5-6mm play at most). the noise should be forever gone ;)

If it returns and your belt is still tight... give us a shout and i'll have another think :P

-
-Jvr

[Deano]

The noise was noticable at spool up then when in the air (150ft) I didn't hear it but just noticed the tail kicking. Seemed like it didn't want to turn very easily. I will have a look at it again. Does anyone know about what temp the boom will begin to shrink??

[flyinfool]

The boom is always changing length with any temp change.
I would start watching and checking when the temp change is more than 30*F from what it was when you tightened it.